Tuesday, April 25, 2017

Antarctica is melting faster than originally thought, new study finds

Researchers at Columbia University's Earth Institute have discovered
that the melting of the Antarctic ice is happening at a much faster rate
than previously believed.

The researchers, who published in the journal Nature, found
enormous amounts of meltwater in places where they didn't expect it,
including a 400-foot-wide waterfall on the Nansen ice shelf.

Previously, meltwater was believed to have been confined to the
northernmost reaches of Antarctica, the parts that are warming the
fastest. The extensiveness of the ice melting could cause sea levels to
raise much faster than previously projected, particularly as they
increase the likelihood of chunks of the ice shelf breaking off
entirely.

"This is not in the future - this is widespread now, and has been for
decades," said lead author Jonathan Kingslake, a glaciologist at
Columbia University's Lamont-Doherty Earth Observatory. "I think most
polar scientists have considered water moving across the surface of
Antarctica to be extremely rare. But we found a lot of it, over very
large areas."

Melt streams were discovered in Antarctica during the early 20th
century, and since then a network of 700 seasonal systems of ponds,
channels, and streams have been discovered. "Now, looking forward, it
will be really important to work out how these systems will change in
response to warming, and how this will affect the ice sheets."

"This study tells us there's already a lot more melting going on than we thought," said coauthor Robin Bell, also with Lamont-Doherty. "When you turn up the temperature, it's only going to increase."

Meltwater typically refreezes in the winter, meaning that the ice shelf
should remain stable for the moment. However, this isn't expected to
continue forever — if too much of the ice melts, the land-bound glaciers
will be allowed to escape into the ocean.

For instance, the Larsen Ice Shelf has lost two large pieces into the
ocean as a result of warming, with a third on the verge of cracking off.